Thermostatic switch



Dec. 7, 1954 v. E. ONEILL THERMOSTATIC SWITCH Filed Aug. 10. 1953 l 'IIIII. VI 'I "Will,

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United States Patent THERMOSTATIC SWITCH Vincent E. ONeill, Taunton, & Controls Corporation, tion of Massachusetts Mass., assignor to Metals Attlehoro, Mass., a corpora- This invention relates particular to manually switches.

In the manufacture and use of manually resettable trip-free thermostatic switches of the kind disclosed in the John D. Bolesky United States Patent No. 2,199,388, difficulty is sometimes experienced in the adjustment and operation of the push plate (or reset plate) therein which is used to reset the snap-acting thermostat plate after it has opened thermally. The difficulty is experienced when the reset plate shown in said patent is applied to snap-acting elements of the type shown in the Victor G. Vaughn et al. Patent No. 2,317,831. In some cases, both contacts carried by the snap-acting element may not reset at approximately the same time. That is, sometimes so-called one-ear action is experienced, namely, that when the reset plate ispushed against the snap-acting element, one side of the element will close first, to be followed by the other side. When this action is encountered, it is found more difiicult to adjust the temperature at which the snap-acting element resets to its cold position, and thus the cost of the switch as a whole is increased. In addition, the resetting temperature cannot be calibrated as accurately as desired.

Therefore, it is one object of this invention to provide an improvement over the thermostat shown in said Patent No. 2,199,388 wherein an improved resetting plate is employed.

Another object of this invention is to provide a resetting plate for such thermostats of improved operating characteristics.

A further object of the invention is to provide a reset plate for use in thermostats of the type described, whose construction is such as to render more easily adjustable the resetting temperature of the snap-acting element.

Other objects and advantages will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which two of various possible embodiments of the invention are illustrated:

Fig. l is a plan view of one embodiment of the reset plate of this invention;

Fig. 2 is a sectional elevation Fig. 1, taken in the direction of Fig. 1;

Fig. 3 is a side view of a thermostat embodying the reset plate of Fig. 1;

Fig. 4 is a bottom view of the thermostat of Fig. 3;

Fig. 5 is a sectional elevation of the thermostat of 2, taken in the direction of sight lines 5-5 on Fig. 6 is a plan view of the Fig. 3 the push-button removed; I

Fig. 7 is a plan view of another embodiment of the reset plate of thisv invention; and

Fig. 8 is a section of the Fig. 7 reset plate taken in the direction of sight lines 88 on Fig. 7.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now to the drawings for a more detailed to thermostatic switches, and in resettable trip-free thermostatic of the reset plate of sight lines 22 on thermostat, with description of the invention, numeral 2 indicates a reset plate of this invention, preferably made of steel or some other rigid metal, although a molded synthetic resin may also be used. A central hole 4 is provided in the plate for the purpose of mounting it (as will be described below) in a thermostatic switch. The plate has been shown in somewhat diamond-like shape, but can have other shapes adapted to fit the particular geometry of the thermostat in which the plate is to be used, if desired.

Provided in the plates are the four raised projections or bosses 6, 8, 10 and 12. As will be described below, these four bosses apply the force and motion of the reset plate, when manually actuated, to four localized areas on the snap-acting plate to reset it. If desired, more bosses may be provided, but four is the minimum.

Referring now to Figs. 3-6, there is shown a thermostat indicated generally by numeral 14 and having a base 16 which is made of electrical insulating material such as Bakelite or other molded resin of proper characteristics. Three stationary terminals 18, 20 and 22 are provided in the base as shown, these terminals being inserted in molded slots in the base, for example, and having overturned heads in the interior of the base to act as stationary contact plates. A threaded adjusting screw 24 is provided in the center of the base 16 (for example, in a threaded hole 26 provided for that purpose). An elongated stem 28 is provided at the upper end of the mounting screw 24, and on stem 28 are respectively mounted a collar 30 and reset plate bushing 32. Bushing 32 slides on collar 30. The turned-over head 34 of stem 28 serves to hold these elements in place in the manner described in the aforesaid United States Patent No. 2,199,388. A thermostatic snap-acting element 36 is held freely but not too loosely on the top of adjusting screw 24 as shown by means of properly spaced shoulders and abutments on the adjusting screw, cooperating with the bottom of collar 30. The reset plate 2 is fastened to the reset plate bushing 32 by means of the shoulderand-riveted construction 38 as shown, the end of bushing 32 being riveted or swaged over in conventional manner. A reset knob 40, preferably made of electrical insulating material such as Bakelite or other molded resin, is pressfitted to the outside of reset bushing 32 so that actuation of button 32 moves reset plate 2. A compresison-type spring 42 is provided inside the reset button 40 to bias the knob 40 upwardly (as drawn). Thus, spring 42 serves to hold the reset plate 2 away from the snap-acting element 36 in its normal position. Other details of the thermostat construction will be found in said U. S. Patents 2,199,388 and 2,317,831.

Referring now to Fig. 6, there is shown a plan view of the Fig. 5 thermostat but with the push button 40 removed in order to show more clearly the relationship between the reset plate 2, the bosses 6, 8, 10 and 12, and the electrical contacts of the switch. As shown in Fig. 6, the inside wall of the base 16 is provided with the recesses 44 which are adapted to receive the ears 46 of the snap-acting element 36 so as to keep the snapacting element from turning on the adjusting screw 24, and thus keeping contacts 52 and 54 aligned with the co-operating contact faces of terminals 22 and 20, contacts 52 and 54 being welded to snap-acting element 36 as shown. Similarly, recesses 48 are provided which are adapted to receive the ends of the reset plate 2, and keep the latter from turning. (Snap-acting element 36 may be of the kind described in said Vaughn et al. Patent 2,317,831, and as indicated above, has the ears 46 which carry thereon the contacts 52 and 54.) In the cold or closed position of the snap-acting element 36, contact 52 makes electrical conenction with the head of terminal 22, and contact 54 makes electrical connection with the head of terminal 20. If desired, an electrical heater 56 may be provided for heating the plate 36, and extends from terminal 20 to terminal 18, the heater being welded to the underneath surface of the turned-over inner heads of these terminals.

In the arrangement shown, it will be observed that bosses 6 and 8 lie on one side of a center line through the center of the thermostat (vertically as drawn), and bosses 10 and 12 lie on the right of said center line This center line is at right angles to the line joining the contacts 52 and 54. It is also to be noted that the bosses are symmetrically disposed in pairs, the position of boss 8 corresponding to that of boss 10, and boss 6 to'boss 1-2: With'thisrelationship, it will beobserved-- in. their'operation. Experience with this constructionhas' shown that it is: at simple operation'. to adjust the temperature of the resetting plate by bending. the plate until; thewcorrect resetting temperatureis obtained;

Referring now to 'Fig. 7;. there is shown another embodiment of the resetting plate. of this invention, which.

differs from. the reset plate;2 in: that. the. bosses.- are. not placed within: the periphery ofthe reset' plate, butinstead are; for-med 'in the plate'edges; Reset. plate 581 again is made; of steel or'some otherrigidi metal or. material, and has-thecentral hole: fiti for, the purpose of mountingitas;aforesaid; The bosses: 62,. 64, 66. andoit are made at theedges of the-resettplate, as shown,. and inthis instance aresillustrated as being quarter spheres. Resetplate' 5'8 is-usedexactly as is thereset plate' Z;

In the. use of either plate.- 2.:or plate 58, the. location of; the bosses: 6-12 inclusive or 62%?) inclusive is such as toaallow that portion of. thesnap-acting element which includes the ears-46v and an adjaeentportion' of the nondevelopable surface oftheelementto snap to the contact open position when thezsnap-acting'plate is-heated, even thoughzthe: reset plate is being held; atits innermost (or resetting) position. Thisaposition issuch that the angle made by" an imaginary; linejoining the: center ofv the snap-acting elementtorrplatei and any boss, is never greater than-45 For'example; theangle which the linejoining boss 6' and the center-of' the plate'limakes with the aforementioned: centenline, is never greater than 45; and

similarlyrthe angle which the linejoiningiboss Swith thev centen-makes with said center. line; is-never: greater than approximately 455%, Thus, the thermostat. is trip-free, that-his, .the--contacts. cannot b'erheld in circuit-closing positionby the resetknobdi): In addition; itis preferred vtohave .the bosses as .far outitowardsthe periphery of the snap-acting plate as :consistent with good manufacturingpractice, bearing inimind the tolerances normally experienced in makingsuch devices inproduction. If thebosses on-each side of the said center line are placed furtheri apart than: shown, that is, each: pair'nearer'the ear: ofz that side of the snap-acting element, it will be foundnthat' the; force required to reset the snap-acting. element to its closed position as. it coolsibecomes'z less, but ontthe other hand, the triprfr'ee"characteristics of theaplate are also'diminished; The mostidesirable setting maybe one orrthez'other, depending onwhat is desired for-the operation of the thermostat. However, it is within the realm of'mechanical skill to determinewhich ismost' suitables. Theresettingtemperature of the snap-acting element-is .adjusted-iby bending the1reset plate so that whenv knob his in its innermost-position; the" element will be deformed-towards its cold position; it.is-desired::to raise=the-temperature--of resetting, plater2. (for example) is bent-so that when knob 40' is at its innermostiposition, the bosses will strain .the element furtherto its cold position. To lower-thezresetting temperature, the resetplate is-bent to strain thesnap-actingelement. less toward itsscold position.

Iri.viewof the. above, it.will beseen that'the several.

objects-ofthe'invention are-:achieved and other advantageous .results attained;

As-irnany changes couldfbe-madein the above constructions Withoutdeparting from the-scope of the invention, it .is intended-that all matter contained in the above description or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. Inthecombinationofa snap-acting thermostatic element and a r1g1d reset plate therefor wherein'said" The result of this; is to cause bothrsidesz That is; if

ricallyoppositeeach other, means-'slidably' mounting-saidreset plate on one side of said snap-acting element whereby said plate may be moved toward or away from one surface of said element; a plurality of bosses protruding from that surface of said reset plate which faces said snap-acting element, a first pair'of said bosses being on one side of a center line extending through the center of said snap-acting element and approximately perpendicular to a line joining said contacts, and a second pair of said bosses being positioned on the other side'o'f'said center line, said paired bosses being positioned on said plate so as to bear against peripheral-portions of said element when said reset plate is pushed against said snapacting element and also being so located that no boss lies on a line through the center ofsaid element which makes an angle greater than approximately 45 with said center line; and means for manually pushing said reset plate against said snap-acting elementa- 2. A thermostatic device comprisinga base; a-snapacting thermostatic element mounted on said base and having two oppositely facing positions of stabilityin' one of whichpositions. it-is located relatively closertry-said; base than it is when in the othenpositiom-said'thermostatic element passing automatically from its said-"closer" position to its said other POSl'tlOH- upon change of ternstaticv element; and spring means urging.-- saidmanual" means to an extended posltion away fIOIn'Sald 61m6I1t,"

said manual means including-plural; means adapted to bear'on the surface of said thermostatic element on eachside ofa center line therethroughwhen said thermostatic elementisinits said other position, to urge said thermostatic element toward'its said closer position,' said center line bBlIlgaPPI'OXlHlfltiY perpendicular to a line joiningsaid first electrical contacts, and said plural means;

comprising a plurality of bossesextending 'from said manual means and overlying said thermostatic element, none of said bosses lying on aline through the center of said elementwhich makes anangle greater than-approximately 45 with said center line.

3. A. manually-resettable snap-acting thermostatic switch comprising a base; stationary contactson said base; a snap-actingIthermostatic element mounted-- on saidbase and havingtwo oppositely facing positions-ofstability in respect to said' base, inone of whichit is nearer to the base thanwhen in the other; electrical-- contacts mounted on said element and electrically engaging said stationary contacts when the element is in its saidnearer position; a rigid reset plate movably mounted on said base and movable toward and away from the thermostat element, said plate having four bosses on its surface extending toward said'element, two of said bosses being on one side =of a line through the center of said plate which s approximately perpendicular to a line ]O11'11Ilg said contacts on said element; and the 'other two being on the other side thereof, said bosses being spaced equi-distantly from the center of said thermostat plate and contactingthe latter on peripheral portions thereof with none of said bosses lying on a line through'the" center of said plate which'makes an'angle greater than approximately 45 with said center line; and means for manually moving said reset plate toward said element.

References Cited in the tile of this patent 1 UNITED STATES PATENTS Number 

